As coronavirus cases surge in the United States and elsewhere, with little relief in sight, the world got good news on Monday. Pfizer and its partner, the German company, BioNTech, announced preliminary results that suggested their vaccine was more than 90 percent effective.

The news — the first results from any late-stage vaccine trial — buoyed stock markets and spirits as the public saw a glimmer of hope. But it’s worth noting that the news is still preliminary, and there is much that is still not known about how well the vaccine works.

And one thing remained clear: The vaccine will not come in time to rescue the world from the next several months, when the virus will take many more lives unless the public takes more stringent public health measures.

Here’s what we know, and don’t know, about the vaccine.

What did these scientists find out?

In July, Pfizer and BioNTech initiated a late-stage clinical trial on a coronavirus vaccine. Half of the people got the vaccine, while the other half got a placebo of salt water. The companies then waited for people to get sick to determine if the vaccine offered any protection.

So far, 94 participants out of nearly 44,000 have gotten sick with Covid-19. An independent board of experts looked at how many of those people got the vaccine, and how many got the placebo. That early analysis suggests the vaccine is over 90 percent effective.

As is standard for clinical trials, the data was “blinded,” meaning that no one except the independent board — not the volunteers, doctors, or the company’s top executives — knows how many of the 94 people sickened by the virus got the vaccine or the placebo. Given the estimate that the vaccine is over 90 percent effective, however, we can safely assume very few people who were vaccinated got Covid-19.

Is that a good result?

It is. The Food and Drug Administration had set a bar of 50 percent efficacy for vaccine makers who wanted to submit their candidates for emergency authorization. If the preliminary results from Pfizer and BioNTech bear out — and accurately reflect how the vaccine will work in the real world — then it’s far more protective than that.

Read more here.